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nozzzle clogged with soot

Posted by blabberjack 
nozzzle clogged with soot
August 14, 2014 07:00PM
hello, as a result of misdiagnosing an extruder problem, I pushed extruder temps higher and higher, causing my nozzle to eventually become clogged with soot. (I suspect the original problem was that when I assembled my e3d hotend, I did not tighten the threaded parts together sufficiently allowing the pla to ooze into spaces between the parts and increase nozzle pressure)
I tried to clean out the pla with a blowtorch but it has not cleaned the small bronze die at the end of the unit, it is in there tightly enough that I can't dislodge it with filament and it does not seem to be burning out at any great rate, I'm worried about degrading the bronze so I don't want to heat it for extended periods.
Should I just keep the heat on the nozzle until all the carbon is burned out?
Re: nozzzle clogged with soot
August 14, 2014 08:00PM
I can tell you from today's tests that PLA won't burn completely. I don't have full/scientific proof, but I think you made your problem worse by burning it. PLA degrades especially well with too high heat, becoming brittle. In my mind that kind of change means it won't burn fully.
I'm not even sure it would all get out once you can get a flow going, again without real knowledge just guessing, it would be in a state that wouldn't be dissolvable.
A common trick is to use guitar string. For 3mm hotends some use toothpicks.

Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus
Re: nozzzle clogged with soot
August 15, 2014 11:19PM
You could always check the local hardware store for "MEK Substitute" (NOT MEK-- MEK is kind of nasty), aka "Ethyl Acetate". People have been having good luck smoothing / melting PLA with it, and it shouldn't harm the nozzle.
Re: nozzzle clogged with soot
August 15, 2014 11:39PM
PLA doesn't burn completely on it's own, but with a proper heat source it cooks off nicely.

I put my clogged (PLA) nozzles over the flame of an alcohol lamp for a few minutes, and all that's left is a light coating of soot, which is easily removed with soap & water (ultrasonic cleaners help a lot!).

This technique has worked well for me with nozzles smaller than .2mm .
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